Evaluation of the inter-person variability of hazards to the users of BAHA hearing implants caused by exposure to a low frequency magnetic field

Abstract

The results support the need to assess the electromagnetic fields hazards to individual implant user exposed to the magnetic field at a level approaching the exposure limits set by international guidelines.

Electromagnetic Energy Absorption in a Head Approaching a Radiofrequency Identification (RFID) Reader Operating at 13.56 MHz in Users of Hearing Implants Versus Non-Users

“…Investigations were carried out using numerical models of structures of two types of bone conduction hearing implants: Bonebridge (MED-EL, Austria) and bone anchored hearing aid (BAHA) (Cochlear, Sweden) [1,2,3,4,5]. In the numerical models of both implants, the dimensions, shape, and material parameters (conductivity and relative permittivity) were taken into account for elements of both the external and the internal parts.…”

“…The head of the hearing implant user or non-user was modeled as a multi-layer ellipsoid with dimensions corresponding to the dimensions of the 5th, 50th, and 95th percentile male head of the Polish population [1,2,27]. The thicknesses of particular tissue layers were the median values of people being implanted with hearing implants: 4 mm for skin, 4 mm for fat, and 9 mm for skull bone.…”

“…Conductive hearing loss can, in various cases, be compensated for by bone conduction hearing implants of the Bonebridge or bone anchored hearing aid attract (BAHA) types (implanted behind the earlobe), which use sound waves conducted through the skull bones directly to the inner ear, where they are perceived in the same way as natural sound. They are electronic devices consisting, among other things, of an acoustic sensor, an audio processor, other electronics, a system of wireless trans-skin signal transmission, magnets, a vibrating system, and titanium elements screwed to the skull [1,2,3,4,5]. The mentioned implants work in different ways.…”

“…The effects of exposure to EMF in tissues adjacent to hearing implants have been already tested using numerical models of exposure to low frequency EMF from medical devices. In that case it was found that the strength of the electric field induced in tissues adjacent to the implant was up to 4.5-times higher in the case of a BAHA implant user (and up to 3.4-times higher in the case of a Bonebridge implant user), in comparison to the values obtained in these tissues in a person without an implant [1,2]. Additionally, the results of this studies showed that the relative effects of exposure to low frequency EMF in implant users depends on the spatial distribution of the EMF influencing the tissues adjacent to the implant, which is the function of the EMF source location against the implant.…”

Modelling the Influence of the 2.4 GHz Electromagnetic Field on the User of a Wearable Internet of Things (IoT) Device for Monitoring Hazards in the Work Environment

“…Due to the considered exposure scenarios in which the RF module is located close to the head, the study was limited only to the numerical model of a head. The head was modelled as a multi-layer ellipsoid with dimensions corresponding to the dimensions of the 50th percentile male head of the Polish population; for more details see [7]. The model includes layers with dielectric parameters @ 2450 MHz frequency adopted from the IT'IS (Information Technologies in Society) Foundation Database of Tissue Properties corresponding to the: skin with an electric conductivity of 1.464 S/m and a relative permittivity of 38.0; subcutaneous adipose tissue (SAT)/fat tissue (0.268 S/m and 10.8); bone (skull bones) (0.394 S/m and 11.4) and internal part corresponding to brain grey matter (1.808 S/m and 48.9) [8].…”